head first servlets and jsp

is used here, that's not good. Target JSP to which the request was forwarded (HANDLEIT.JSP)Why the first request did not print out the "Welcome to Out page!" This sentence before jumping to judge the text?Because, using the Jsp:forward standard action, the buffer is emptied before forwarding, that is, all content that is written to the response before forwarding will be cleared out.If there is a good person, in the "Welcome to Out page!" After th

good to put servlets, declarations, and expressions in a JSP:1) Web page designers should not be required to understand Java2) Java code in JSP is difficult to modify and maintainThe user of EL (Expression Language) provides an easier way to invoke Java code, but the code itself is placed in place.The code might be in a normal Java class, perhaps a JavaBean, a c

elements 6 true7 Scripting-invalid>8 Jsp-property-group>9 Jsp-config>Ten Web-app>Ignore El in JSP:method One : Specify in Web. xml:1 Web-app>2 Jsp-config>3 Jsp-property-group>4 Url-pattern>*.jspUrl-pattern>5 el-ignored> //This flag indicates that the EL is ig

("Fred"); Names.add ("Pradeep"); Names.add ("Philippe");Req.setattribute ("Names", names); RequestDispatcher View= Req.getrequestdispatcher ("result.jsp"); View.forward (req, resp); }}result.jspImport= "Java.util.List"%>Import= "Java.util.Iterator"%>Created by IntelliJ. USER:XKFX Date:2017/6/14Time :17:27 to change ThisTemplate Use File | Settings |File Templates.--%>//response.setcharacterencoding ("Utf-8");%> List Names= (List) request.getattribute ("names"); Iterator it=Names.iterator ();

"Head First Servlets JSP" (Chinese version) Bb,ks BB, Su Yu, Lin Jian, China Power PressData interactionWeb browsers and Web servers: Interact with HTML data through the HTTP protocol.What exactly is MIME type?To an HTTP response:The value of the Content-type (content Type) response header is called the MIME type.The MIME type tells the browser what type of dat

particular protocol to handle the secure transmission. (The HTTPS protocol on top of SSL is practically always used.) ）Data protection has some overhead and does not encrypt every request and response in your app, so use--conservatively and declaratively--to achieve data confidentiality and integrity:Data protection Unauthenticated customer requests a restricted resource without a transmission guarantee An unauthenticated customer requests a restricted resource, which is guaranteed

implementation and pass it through the Chain.dofilter () call to the servlet. And this custom implementation must also include a custom output stream, as this is our goal, and the filter can get this output after the servlet writes the output and before the output is returned to the customer. Disadvantage: Complex httpservletresponse interfaces need to be implemented, but usually not. To achieve their own httpservletresponse too responsible, how to do? --servlet Packaging DeviceCr

(ServletContext, HttpS ... ) is exactly the same as the property APIFor enumeration, see Java-enumeration Summary by IAMTJW5, the bad side of the property. •. ```.. ``.. `.`.`...`.. Context properties are not thread safe! A context property may be changed and accessed by multiple servlets at the same time. The bad solution is to add synchronized to doget (or other methods), which does not solve the problem because synchronized can only preve

example The life cycle of a simple tag processorCustomize a simple tag with attributes (like C:foreach? ）Stop page Processing--skippageexceptionStop page processing, not just throwing exceptions, but expecting the first part of the page to be processed as a response, but not the latter part of the process for some reason.The page information after the visible tag (back in the page ...) has no output!What happens if a tag is called from a contained page?Skippageexception just stops calling

custom tag, then now a little bit to see how the tag's support code is written. The Java class that completes the tagging work Foo.AdvisorTagHandler.javaThis simple markup processor extends the Simpletagsupport and implements two key methods: Dotag () and Setuser ().Dotag () is the way to do the work, and SetUser () is the method that accepts the value of the property. Details are as follows: El function vs Tag processor Are all Java classes Need to be pla

("); org.apache.jasper.runtime.JspRuntimeLibrary.include (Request, response, "footer.jsp", out, false ); Out.write ( "\ n"); Out.write ("\ n"); Out.write ("The bold distinction is the conversion code for the include directive and the include action.Param actionModify the index.jsp code above:Modify Footer.jspEffectFoward ActionGarbled problem is not resolved, can only input Chinese. (Request.getparameter ("UserName")null) {% > page= "handleit.jsp"/> %}% > handl

; Servlet-class>Com.example.ListenerTesterServlet-class> servlet> servlet-mapping> Servlet-name>ListenertesterServlet-name> Url-pattern>/listenertester.doUrl-pattern> servlet-mapping> Web-app> packagecom.example;Importjavax.servlet.ServletContext;Importjavax.servlet.ServletContextEvent;Importjavax.servlet.ServletContextListener; public class Myservletcontextlistener ImplementsServletcontextlistener {@Override public voidcontextinitialized (servletcontextevent serv

client. Resp),doPost (httpservletrequest req, HttpServletResponse resp) such as The servlet responds to the customer by responding to the object, and the container returns the response to the customer. The service () thread ends, retains or cleans up the responding object, and the customer gets a response. 3. Mark Tomcat Official document Servlet API documentation4, HttpServlet inheritance tree, interface Java.lang.Object Javax.servlet.GenericServletJavax.servlet.http

;Importjavax.servlet.*;Importjava.io.IOException; Public classFilterImplementsjavax.servlet.filter{Private intvisited; @Override Public voidInit (Filterconfig filterconfig)throwsservletexception {} @Override Public voidDoFilter (ServletRequest servletrequest, Servletresponse servletresponse, Filterchain filterchain)throwsIOException, servletexception {servletresponse.setcontenttype ("Text/html"); Servletresponse.setcharacterencoding ("Utf-8"); Visited++; Filterchain.dofilter (ServletReque

configuration in Assigning values to Objects Provided ServletConfig when the servlet was first initialized Provided ServletContext when the servlet was first initialized To initialize the parameters Servletcontextlistener (Context Listener)Servletcontextlistener is able to listen to a context initialization event so that it can get context parameters and run some code before the app provides services to the customer.Just as you tell the Web container

Let other components take over all requests; Partial takeover requestSome questions--The Intercept point is useful.1. Let other components take over all requests. PackageCom.example.web;ImportCom.example.model.BeerExpert;Importjavax.servlet.*;Importjavax.servlet.http.*;ImportJava.io.*;ImportJava.util.*; Public classBeerselectextendsHttpServlet {@Overrideprotected voidDoPost (httpservletrequest req, HttpServletResponse resp)throwsservletexception, IOException {String C= Req.getparameter ("Color")

Declaring a generic error pageThis applies to all resources in the Web app, not just the JSP A more explicit exception error declaration Declaring error page based on HTTP status code Configuring servlet initialization in DDThe servlet is initialized by default when the first request arrives, and you can set the Load-on-startup element if you want to load the servlet when the deployment or server restarts.If multiple elements ar

1, El's English is expression Language, translated into Chinese is "expression language." This is a scripting language for front-end programmers, and El does not have a "big difference" compared to Java expressions, and it seems somewhat "superfluous" to the backend programmer.2, however, We can not force every front-end programmer to learn Java,el compared to java, the cost of learning is lower and easier to understand.3, in the previous written code practice test, first put scriptlet to ban, (

;/cookietest.doUrl-pattern> servlet-mapping> servlet> Servlet-name>CheckcookieServlet-name> Servlet-class>Com.example.web.CheckCookieServlet-class> servlet> servlet-mapping> Servlet-name>CheckcookieServlet-name> Url-pattern>/checkcookie.doUrl-pattern> servlet-mapping>Web-app> PackageCom.example.web;Importjavax.servlet.ServletException;Importjavax.servlet.http.*;Importjava.io.IOException;ImportJava.io.PrintWriter; Public classCheckcookieextendsHttpSe

is not serializable? For migration, the Property object class needs to be httpsessionactivationlistener and the activation/deactivation callback method is used to solve the problem. Listener Example Session counterThis listener allows you to track the number of active sessions in this web app:To configure listeners in DD:Attention: Attribute Supervisor ListenerThis listener can be traced every time a property is added to a session, a property is deleted, or a property is repla